I'm not sure about how big the baby could be I think it would just depend on your body and what you eat. And I started to feel my baby's movements at 19 weeks but everyone is different .
It's all up to your baby! I don't the size you or your partner where at birth matters.
As for the movements, usually for your first baby people will tell you anywhere between 18-20 (maybe later), but this is my first baby and I can feel slight movements now at 15 weeks... It completely depends on baby and you :)
I don't think it's true mainly cause I was born 4lbs 11oz and yet I'm 37weeks with my son and he is already pushing 6lbs. As the ladies stated above, every baby and pregnancy is different.